Method of treating bagasse



Feb. 23, 1932- w. L s, WILLIAMS 1,847,050

METHOD OF TREATING BAGASSE Filed April l9 v 1930 '2 Sheets-Sheet 1 Feb. 23, 1932 w. s. WILLIAMS 7 1,847,050

METHOD OF TREATING BAGASSE Filed April 19 1930 2 Sheets-Sheet 2 19 M M 1 Z3 f x f H q n K J 5 v v v g'wventoz l mented Feb. 23, 1932 KlNITED TATES PATENT OFFICE WILLIAM L. S. WILLIAMS, OF HI'LO, TERRITORY OF HAWAII, ASSIGNOR T HAWAIIAN CANE PRODUCTS, LTD., OF HILO, HAWAII, A CORPORATION OF HAWAII METHOD or TREATING BAGASSE Application filed April 19,

This invention relates to a process of treating bagasse fibers for use in the manufacture of wallboard therefrom. More particularly, this invention relates to the preparation of bagasse fibers whereby a wallboard of extreme lightness and high .strength may be manufactured.

' The terrn bagasse as used herein refers particularly to the pithy fibers obtained as a residue after the extraction of juices from various varieties of sugar cane. In its broader aspect the term bagasse as used herein may be said to include all fibers or vegetable fibrous materials obtained from growths including a pithy center or core.

Attempts havebeen made ever since about 1906 to produce fibers from various pith-containing materials for the manufactureof continuous sheets of material, and various processes to make wallboards from bagasse fibers have been disclosed since about that time.

The process of this invention :difiers from the prior processes in that a new and novel sequence of steps is employed, whereby a fiber is produced characterized by its freedom from pith, thereby permitting the manufacture of a strong, light, clean wallboard.

Heretofore, it has been thought necessary to retain the major portion of the )ith or other intercellular matter upon the bers so as to form knobs or protuberances thereon A which engage with each other during the felting process employed during the formation of the wallboard.

An object of this invention is to disclose and provide a process of treating fibrous material obtained from the stalks of pithy plants, so as to produce fibers substantially free from pith. 4

Another object is to disclose and provide a process of treating bagasse fibers whereby soft and pliable fibers substantially free from pitch and adapted for use in the manufacture of wallboard therefrom are produced.

Another object is to disclose and provide a method of treating bagasse fibers whereby the pithy intercellular constituents are re-' moved therefrom without employing large quantities of chemicals or injuring the fibers.

A still further object is to disclose and pro- 1930. Serial no. 445,783.

vide a method of treating bagasse fibers whereby the major portion of pith adhering of one form of means for separating the major portion of the pith from the fibers.

Figure 3 is a' side elevation, partly in section, of a. digester employed in'carrying out the process.

Figure 4 is a side elevation, partly in section, of a stripping and shredding mechanism used in carrying out the process of this invention.

The preferred process of this invention is applied to sugar cane fibers or bagasse which is obtained by shreddingand crushing sugar cane for the extraction of juices therefrom. The crushed and shredded fibers are generally sprayed with water to fully remove the I sugar contained therein, and if desired may be dried partially to remove excess water before being treated in accordance with this method.

' The fibers are preferably first passed over one or more screens 1, preferably of the vibratory type so as to remove the major portion of the pith from the fibers. The shredded bagasse may be supplied to the vibrating screens 2 by means of a blower 3, a hood 4 covering said screens so as to force the lighter particles of pith through the meshes of the screens 2.

The pith may be collected in suitable chambers 5 from hoppers 6 which discharge by means of lines 7 into such hoppers. Screened air outlets '8 may be ,provlded m the chambers 5. The screens 2 may be v1- brated in any suitable manner, as for ex-* ample, by meansof motors 9 mounted centrally ofv said screens 2.

The fibers discharged from the screens 2 by means of a pipe or spiral conveyor 10 still contain a minor proportion of pith,

which is tenaciously held by the fibers. The fibers may then be cooked in digesters 11, which are preferably cylindrical or spherical in form and are capable of rotation; One' form of digester which may be employed is shown in Figure 3.

In the digester 11 the fibers are cooked at a temperature of between 275 and 350 F., and preferably at a temperature of from about 300 to 320 F., and at a pressure of from about 60 to. 80 lbs. WVhen a pressure of about 70 lbs. is employed and a temperature of between about 300 and 320 exists in the digester, the cooking should be continued for a period of about four hours. About 4: to 6% of lime, by weight of the fibers, is added to the mass in the digester with each charge, and the cooking continued for aperiod of time sufficient to substantially dissolve all of the encrusting material on the fibers. During such cooking the pith dissolves partially or becomes soft. This soft pith is stripped from the fibers mechanically, such stripping being accomplished by the abrasion of the mass of fibers within the digester against the scrapers positioned therein. It is to be understood that the digester is rotated during the cooking operation.

Attention is here called to the fact that a relatively small quantity of alkali, such as lime, is employed and lime is preferably used inasmuch as caustic soda produces a'harsher and more brittle fiber.

The digester 11 may be spherical, as shown in Figure 3, and be provided with trunnions 12 journaled in bearings 13 mounted on supporting pillars 14. One of said trunnions may be provided with a suitable gear 15 driven by a suitable chain of gearing, and a source of'power, not shown. The shell of digester 11 may be provided with a manhole 16 whichmay beremovably attached thereto, thereby permitting the digester to be charged with the bagasse and lime.

The interior of the digester 11 may be provided with a plurality of battles 17 attached to the interior of the digester 11 and adapted to act as agitators for the bagasse within said digester. The number and arrangement of b'afiles may be varied, but such baflies should be primarily designed to thoroughly agitate the contents and at the same time'strip the softened pith remaining on the fibers from the fibers.

From the digester 11, after the cooking operation, the cooked pith is sent into a washer 18 and dissolved pith and extracted matter. is removed from the cooked fibers. The fibers are then conveyed in any suitable manner into one or more pulpers 19, which may be of any desired construction and preferably of the character shown in Figure 4. The fibers may be admitted into the pulper 19 by means of a conduit 20 leading to the center portion of an attrition disc 21. Opposing the attritiondisc 21 there may be a secondary disc 22.

' Such secondary disc 22 may be mounted upon a shaft 2.3 extending through the housing of the pulper 19, such shaft being driven in any desired manner as by means of a motor 24. The disc 21 may also be mounted upon a shaft 25 and driven as by means of a motor 26. The direction of rotation of the two discs 21 and 22 may be the same, and they may revolve in opposite directions, but in all instances the two discs must move relatively to each other. Preferably, the discs 21 and 22 are driven in opposite directions.

The disc 21 may be provided with one or more ports 27 adapted to communicate with the inlet conduit 20. \Vater and steam inlets 28 may be positioned in the housing of the pulper 19, such inlets being directed toward the apertures 27 The discs 21 and 22 are spaced from each other and may be provided with removable facings 29 and 30, such facings being suitably corrugated' or ribbed, but the cooked fiber fed to the pulpers through conduit 20 passes into the space between the discs 21 and 22 through apertures27, and is then discharged radially throughthe space existing between facing plates 29 and 30 into the outer portion of the pulper 19, from which the pulp fiber is then discharged through conduit 31. During passage through the pulper and particularly between the facing plates 29 and 30, the fiber is stripped of any pith remaining thereon. Simultaneously, the fibers are separated from each othen,

From the pulpers the pulp may be sent to screens 32, the excess water being returned to the pulpers as by line 33. The screened fibers may then pass to a decker 34 in which the freeness of stock is brought down to about 35 seconds (as tested with a standard freeness tester). The fibers are then sent to sizing tanks 35 supplied with suitable sizing materials from supply tanks 36. It has been determined that about 2% rosin sizing followed by the addition of about 4% alum to set the sizing on the fibers, these percentages being calculated on the dry fiber, produces satisfactory results. The sized pulp may then pass to forming machines 37, and from such forming machines into a suitable board making machine 38. i

The board making machine may be of the type known as the Downington, and the board formed thereon may pass to suitable saws 39 and the lengths of finished board then sent through a drier 40. The dried board may then be sent through saws 41,

. Where the boards are accurately trimmed to size. The white water from the forming machine 38 may be returned to a settling tank or, suitable reservoir 42, and added to the decker 38 in quantities required to maintain the pulp at the required consistency.

"It will be thus seen that the characteristic of the method employed and described hereinabove is the removal and separation of pith and incrusting material from the fibers, such removal being accomplished at three distinct points in the process of preparing the fibers for use in wallboard.

The major portion of the pith-is removed by the screening operation, but additional quantities of pith are removed during the cooking and during the pulping. rior methods of preparing bagasse or other pithy fibers for use in the manufacture of paper have relied entirely upon the solvent action of alkalis on the pith, but it has been found that if alkalis are employed in sufiicient quantities to actually remove all of the pith, the texture, strength and flexibility of the fiber is materially reduced, and such fibers, although capable of being used in the manufacture of very poor qualities of paper, can not be used for wallboard manufacture.

By employing only small quantities of an alkali such as lime (specifically, only about 4 to 6% of lime on the weight of the fibers), the pith and incrusting matter is softened sufliciently to permit the removal of the pith by bafiies positioned Within the cooker and against which the fibrous material is thrown during the cooking operation, and furthermore by the action of the pulper. 1

Furthermore, by employing only a small quantity of lime, the fibers are not weakened appreciably and are not disintegrated or cut up into very short lengths by the ulper. Instead, they are readily separated thereon. The uality of the resulting fiber is evidenced by the quality of the finished wallboard. A wallboard made from fibers produced in accordance with this invention is stronger than wallboard made from bagasse fibers in accordance with the prior art processes. Furthermore, the wallboard is lighter in weight and for this reason has greater eflectiveness as a heat insulating medium.

Details of the forming presses, deckers and other apparati used in carrying out the manufacture of wallboard have not been disclosed hereinabove, inasmuch as such units'are well known in the art.

Although certain specific forms of apparatus have been described hereinabove, such is merely for illustrative purposes and it is to be understood that the invention is not limited thereto, but instead includes all such modifications and changes as come within the scope of the appended claims. 4

1. In a method of treating bagasseior the production of fibers to be'used in themanu facture of wallboard, the steps of subjecting bagasse to a screening operation to remove pith particles therefrom, cooking the bagasse with 4 to 6% of lime at a superatmospheric rom each other by the Y pulper and stripped of any residual pith pressure for a period of time sufiicient to dissolve incrusting material and substantially all pith remaining on said fibers, stripping pith from said fibers during cooking by mechanical abrasion, washing the cooked fibers to remove dissolved pith and extracted matter, and then pulping the cooked .fibers and simultaneouslyseparating any pith remaining thereon.

2. A method of treating bagasse for the production of fibers to be used in the manufacture of wallboard, comprising subjecting bagasse to 'a screening operation to remove pith particles therefrom, cooking the ba-gasse with 4 to 6% of lime at a pressure of between about 60 and 80 lbs., for a period of time sufiicient to dissolve incrusting material and substantially all pith remaining on said fibers, stripping pithfrom said fibers during cooking by mechanical abrasion, washing the cooked fibers to remove dissolved pith and extracted matter, and then pulping the cooked 

